In the present specification the spatial configuration of the substituents related to the chiral carbon atom denoted with ".alpha." is characterized by "S" and "R", respectively The designations "cis" and "trans", respectively, mark the position of the substituents attached to carbon atom "3" of the cyclopropane ring related to the spatial configuration of the substituents of carbon atom "1". The absolute spatial configuration of the substituent attached to carbon atom "1" is denoted with the prefix "1R" and "1S", respectively.
In the present specification the various enantiomers and enantiomer-pairs are designated with the following abbreviations:
______________________________________ Ia mixture of 1RcisS and 1ScisR Ib mixture of 1RtransS and 1StransR Ic mixture of 1RcisR and 1ScisS Id mixture of 1RtransR and 1StransS If 1RtransR Ig 1RtransS Ih 1ScisR Ii 1StransR ______________________________________
It is known that pyrethroids of the Formula (I) known under the generic name "cypermethrin" belong to the valuable family of synthetic pyrethroids and are useful as insecticides (Hungarian Patent No. 170,866). These compounds may be prepared by reacting m-phenoxy-benzaldehyde cyanohydrin with the corresponding cyclopropane carboxylic acid chloride in the presence of a base [Pestic. Sci. 6, 537 - . . . (1975)]. The product thus obtained consists of eight stcreoisomers i.e. of a mixture of four enantiomer-pairs. If a 60:40 mixture of the corresponding trans and cis cyclopropane carboxylic acid chlorides is used, the mixture contains 18-19% of enantiomer-pair Ia, 21-22% of enantiomer-pair Ic, 26-27% of enantiomer-pair Ib and 33-34% of enantiomer-pair Id.
According to prior art the stereoisomers of cypermethrin show different biological activity. It is generally accepted that the activity of molecules comprising cis cyclopropane carboxylic acids is superior to that of the corresponding trans derivatives [Pest. Sci. 7, 273 (1976)].
In the comparative biological tests of various pyrethroids [Pest. Sci. 9, 112-116 (1978)] the cis and trans stereoisomers--including the cypermethrin stereoisomer-pairs--were evaluated together.
The comparative tests were carried out on Musca domestica L. and Phaedon cochleariae Fab species. Concerning the chloro derivatives from the trans isomers activity data of 1RtransS (Ig) and 1RtransR were disclosed. The said data show that--while the 1RtransS isomer possesses a strong activity--the 1RtransR isomer is considerably less active [according to the test the activity related to bioresmetrine (100) amounts to 1400 and 81, respectively, on Musca domestica and to 2200 and 110, respectively on Phae don cochleariae]. It was disclosed furtheron that the activity of a mixture of both tested isomers was lower than the calculated value. Thus the isomers showed an antagonism rather than the expected synergism and the rate of antagonism amounted to 1.42 and 1.46 on house fly and mustard beetle, respectively
As a result of the said tests and publications the trans isomers and mixtures thereof were pushed to the background of biological interest and research was focused to active cis derivatives and mixtures thereof. This led to the development of alphamethrin (isomer mixture of 1RcisS and 1ScisR (Ia) of the chloro derivatives] and decamethrin [comprising the IRcisS isomer (If) of the bromo derivatives].
Similar data were set forth for the bromo derivative; on mustard beetle the rate of antagonism amounts to 1:48.